Dry bulk material, such as grain, compounds, chemicals, pharmaceuticals, fertilisers, minerals, and a combination of such materials, are typically stored in storage containers, such as hoppers, silos and the like. Such storage containers typically have a body configured to receive the material therein, and an outlet provided on a lower region of the body through which the dry bulk material can flow to exit the storage container, typically under the force of gravity.
In agricultural applications, grains such as wheat, barley and the like, are typically harvested from a crop and delivered from the field into large hoppers or silos, where they are stored in a controlled environment. In many instances, hoppers that are provided for the storage of grains typically have an outlet formed in a bottom region thereof that provides an egress point for the grain to be collected for transport and delivery to a variety of end users. Typically, such hoppers comprise a cylindrical body portion having a lower cone region that tapers towards the outlet, which may be located in the wall of the lower cone region. Thus, delivery of the grain from the outlet is achieved under gravity forces whereby the grain behaves like a fluid that flows towards and through the outlet. An auger may also be used adjacent the outlet to assist in extracting the flow of grain from the outlet, to an elevated collection point,
For primary producers, such as grain farmers, it is of primary importance that a storage hopper is fully discharged of grain from time to time. This is important from an economical perspective as the grain has commercial value and it is in the best interests of the primary producer to ensure that maximum profit is obtained from their crops. Further to this, it is also important from a primary producer's perspective to fully discharge a hopper to prevent disease and pest infestation. This may occur when grain is stored in a hopper for long periods, as may happen if the hopper is not fully discharged.
The speed and complete discharge of grain from a silo is also if particular importance to the transport operator responsible for the collection and delivery of the grain from the silo. Transport operators typically operate vehicles having large storage tanks to receive the grain for transport. The transport operators typically collect the stored grain from the storage hoppers located on farms and the like. In order to collect the grain from the storage hoppers the transport operators arrange their vehicles such that the grain flows into their storage tanks from the hopper, typically via an auger or similar conveying device. Many transport operators may be required to attend a number of storage hoppers in a typical work day and in order to provide an efficient collection service, it is fundamental that the time taken to discharge the storage hopper into the storage tanks of the vehicle is minimised. Any blockages of flow of grain from the storage hopper, or reduction in flow can have a significant adverse effect on the efficiency of the transport operator, which may impact the transport operator's financial position through loss of income and generate a cost that may be passed on to the primary producer.
In this regard, a common problem with conventional grain storage hoppers is that the lower cone regions of the hoppers are typically very shallow, making it difficult to fully discharge the hoppers, particularly the last few tonnes of grain that is stored in the silo. In such instances, the grain tends to settle upon the shallow inside walls of the lower cone region such that it no longer behaves like a fluid, but becomes static. Thus, it has been known for many Owners and operators of the hoppers to heavily strike the external walls of the cone region in an attempt to induce flow back into the static grain particles. However, such an action often results in the walls of the hopper becoming damaged or dimpled, which may cause additional problems to the fluid flow of the grain, and thus the future usefulness of the hopper, as the inner surface of the hopper may provide a pitted surface upon which the grains collect.
It has also been known for operators to enter into the hoppers or silos during the discharging process to manually assist in moving the grain toward the outlet, with the use of shovels or other manual means. However, this is a very dangerous practice and presents a significant safety risk to the operator, as an operator may sink into the grain and suffocate, or come into contact with an auger or the like which could cause significant injury, and in extreme cases, death. Further to this, the internal environment of a silo or hopper is often filled with grain dust or husks which could cause considerable harm to the operator's lungs and respiratory system, and which may ignite or become explosive when exposed to a spark.
To address this issue, and to induce fluid flow into the stored particles of grain, a variety of shaking or vibrating devices have been proposed, which attempt to apply a constant vibration to the walls of the hopper so as to impart energy to the grain. Most such proposals are directed towards supplying a dedicated device driven by mains electricity so as to operate at a single frequency, namely mains frequency (50 or 60 Hz). However, as most silos and grain storage hoppers are often located remote from a mains power supply, such devices are not applicable to most grain collection situations and are not portable, so have a limited application.
More recently, a portable device such as that disclosed in the present applicant's co-pending International PCT Application No, PCT/AU2008/000653, the contents of which are incorporated herein by reference, has been proposed. Such a device offers a significant improvement over previous devices by providing a means for monitoring the amplitude of vibration applied, and automatically regulating the frequency and amplitude of the applied vibration in accordance with predetermined characteristics. In particular, such a system sought to detect the resonant frequency of the hopper as the hopper discharges and to control the vibratory stimulus accordingly, such that the stimulus was maintained as close to the resonant frequency of the hopper and contents as possible throughout the discharging process.
However, such an arrangement requires constant delivery of a vibratory stimulus at or around resonant frequency. This has a significant drain on power requirements and has the potential to send the physical structure of the hopper into structural resonance, which may compromise the structural integrity of the hopper.
Thus, there is a need to provide a system of controlling the vibratory, stimulus applied to a storage container, such as a hopper, that maximises the efficient use of the gravity forces to cause fluid flow of the material and which maintains the applied stimulus within safe and predetermined levels, whilst providing complete and rapid discharge of the grain from the hopper.
The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.